MyD88-dependent interplay between myeloid and endothelial cells in the initiation and progression of obesity-associated inflammatory diseases

Immunologic and inflammatory consequences of SARS-CoV-2 infection and its implications in renal disease

The emergence of the COVID-19 pandemic made it critical to understand the immune and inflammatory responses to the SARS-CoV-2 virus. It became increasingly recognized that the immune response was a key mediator of illness severity and that its mechanisms needed to be better understood. Early infection of both tissue and immune cells, such as macrophages, leading to pyroptosis-mediated inflammasome production in an organ system critical for systemic oxygenation likely plays a central role in the morbidity wrought by SARS-CoV-2. Delayed transcription of Type I and Type III interferons by SARS-CoV-2 may lead to early disinhibition of viral replication. Cytokines such as interleukin-1 (IL-1), IL-6, IL-12, and tumor necrosis factor α (TNFα), some of which may be produced through mechanisms involving nuclear factor kappa B (NF-κB), likely contribute to the hyperinflammatory state in patients with severe COVID-19. Lymphopenia, more apparent among natural killer (NK) cells, CD8+ T-cells, and B-cells, can contribute to disease severity and may reflect direct cytopathic effects of SARS-CoV-2 or end-organ sequestration. Direct infection and immune activation of endothelial cells by SARS-CoV-2 may be a critical mechanism through which end-organ systems are impacted. In this context, endovascular neutrophil extracellular trap (NET) formation and microthrombi development can be seen in the lungs and other critical organs throughout the body, such as the heart, gut, and brain. The kidney may be among the most impacted extrapulmonary organ by SARS-CoV-2 infection owing to a high concentration of ACE2 and exposure to systemic SARS-CoV-2. In the kidney, acute tubular injury, early myofibroblast activation, and collapsing glomerulopathy in select populations likely account for COVID-19-related AKI and CKD development. The development of COVID-19-associated nephropathy (COVAN), in particular, may be mediated through IL-6 and signal transducer and activator of transcription 3 (STAT3) signaling, suggesting a direct connection between the COVID-19-related immune response and the development of chronic disease. Chronic manifestations of COVID-19 also include systemic conditions like Multisystem Inflammatory Syndrome in Children (MIS-C) and Adults (MIS-A) and post-acute sequelae of COVID-19 (PASC), which may reflect a spectrum of clinical presentations of persistent immune dysregulation. The lessons learned and those undergoing continued study likely have broad implications for understanding viral infections' immunologic and inflammatory consequences beyond coronaviruses.

Loss of MER Tyrosine Kinase Attenuates Adipocyte Hypertrophy and Leads to Enhanced Thermogenesis in Mice Exposed to High-Fat Diet

Obesity is characterized by low-grade inflammation that originates predominantly from the expanding visceral adipose tissue, in which adipocytes respond to lipid overload with hypertrophy, and consequently die by apoptosis. Recruited adipose tissue macrophages (ATMs) take up the excess lipids and remove the dead cells; however, long-term exposure to high concentrations of lipids alters their phenotype to M1-like ATMs that produce pro-inflammatory cytokines and resistin leading to insulin resistance and other obesity-related pathologies. Mer tyrosine kinase is expressed by macrophages and by being an efferocytosis receptor, and by suppressing inflammation, we hypothesized that it might play a protective role against obesity. To our surprise, however, the loss of Mer protected mice against high-fat diet (HFD)-induced obesity. We report in this paper that Mer is also expressed by adipocytes of both white and brown adipose tissues, and while its activity facilitates adipocyte lipid storage both in vitro and in vivo in mice exposed to HFD, it simultaneously attenuates thermogenesis in the brown adipose tissue contributing to its 'whitening'. Our data indicate that Mer is one of the adipocyte tyrosine kinase receptors, the activity of which contributes to the metabolic decision about the fate of excess lipids favoring their storage within the body.

The innate immune regulator MyD88 dampens fibrosis during zebrafish heart regeneration

The innate immune response is triggered rapidly after injury and its spatiotemporal dynamics are critical for regeneration; however, many questions remain about its exact role. Here we show that MyD88, a key component of the innate immune response, controls not only the inflammatory but also the fibrotic response during zebrafish cardiac regeneration. We find in cryoinjured myd88-/- ventricles a significant reduction in neutrophil and macrophage numbers and the expansion of a collagen-rich endocardial population. Further analyses reveal compromised PI3K/AKT pathway activation in the myd88-/- endocardium and increased myofibroblasts and scarring. Notably, endothelial-specific overexpression of myd88 reverses these neutrophil, fibrotic and scarring phenotypes. Mechanistically, we identify the endocardial-derived chemokine gene cxcl18b as a target of the MyD88 signaling pathway, and using loss-of-function and gain-of-function tools, we show that it controls neutrophil recruitment. Altogether, these findings shed light on the pivotal role of MyD88 in modulating inflammation and fibrosis during tissue regeneration.

Unravelling monocyte functions: from the guardians of health to the regulators of disease

Monocytes are a key component of the innate immune system. They undergo intricate developmental processes within the bone marrow, leading to diverse monocyte subsets in the circulation. In a state of healthy homeostasis, monocytes are continuously released into the bloodstream, destined to repopulate specific tissue-resident macrophage pools where they fulfil tissue-specific functions. However, under pathological conditions monocytes adopt various phenotypes to resolve inflammation and return to a healthy physiological state. This review explores the nuanced developmental pathways and functional roles that monocytes perform, shedding light on their significance in both physiological and pathological contexts.

Bromine/Sulfur-Substituted 9H-Carbazoles Produced by the Marine-Derived Streptomyces sp. OUCMDZ-5511 upon NaBr Exposure

Ten undocumented carbazole derivatives (2-11) along with the reported analogue (1) were isolated from the mangrove-derived Streptomyces sp. OUCMDZ-5511, cultured with NaBr-supplemented liquid medium. Compounds 1-7 are brominated carbazoles, and 8, 10, and 11 feature an additional thiazole or 2,3-dihydro-1,4-oxathiine rings, respectively. Their structures were identified through spectroscopic techniques, computational chemistry, and X-ray crystallography. Notably, compounds 6 and 8 effectively inhibited immune cell migration, indicating anti-inflammatory activity in vivo, potentially via Myd88/Nf-κB pathways, as suggested for compound 6.

Unraveling the complex roles of macrophages in obese adipose tissue: an overview

Macrophages, a heterogeneous population of innate immune cells, exhibit remarkable plasticity and play pivotal roles in coordinating immune responses and maintaining tissue homeostasis within the context of metabolic diseases. The activation of inflammatory macrophages in obese adipose tissue leads to detrimental effects, inducing insulin resistance through increased inflammation, impaired thermogenesis, and adipose tissue fibrosis. Meanwhile, adipose tissue macrophages also play a beneficial role in maintaining adipose tissue homeostasis by regulating angiogenesis, facilitating the clearance of dead adipocytes, and promoting mitochondrial transfer. Exploring the heterogeneity of macrophages in obese adipose tissue is crucial for unraveling the pathogenesis of obesity and holds significant potential for targeted therapeutic interventions. Recently, the dual effects and some potential regulatory mechanisms of macrophages in adipose tissue have been elucidated using single-cell technology. In this review, we present a comprehensive overview of the intricate activation mechanisms and diverse functions of macrophages in adipose tissue during obesity, as well as explore the potential of drug delivery systems targeting macrophages, aiming to enhance the understanding of current regulatory mechanisms that may be potentially targeted for treating obesity or metabolic diseases.

History and future perspectives of adipose tissue macrophage biology

Macrophages contribute to adipose tissue homeostasis; however, they are also thought to be responsible for insulin resistance in obesity. Macrophages, which were oversimplified in past methodologies, have become rather difficult to understand comprehensively as recent developments in research methodology have revealed their diversity. This review highlights recent studies on adipose tissue macrophages, identifies controversial issues that need to be resolved and proposes a scenario for further development of adipose tissue macrophage biology.

The role of immune system in atherosclerosis: Molecular mechanisms, controversies, and future possibilities

Numerous cardiovascular disorders have atherosclerosis as their pathological underpinning. Numerous studies have demonstrated that, with the aid of pattern recognition receptors, cytokines, and immunoglobulins, innate immunity, represented by monocytes/macrophages, and adaptive immunity, primarily T/B cells, play a critical role in controlling inflammation and abnormal lipid metabolism in atherosclerosis. Additionally, the finding of numerous complement components in atherosclerotic plaques suggests yet again how heavily the immune system controls atherosclerosis. Therefore, it is essential to have a thorough grasp of how the immune system contributes to atherosclerosis. The specific molecular mechanisms involved in the activation of immune cells and immune molecules in atherosclerosis, the controversy surrounding some immune cells in atherosclerosis, and the limitations of extrapolating from relevant animal models to humans were all carefully reviewed in this review from the three perspectives of innate immunity, adaptive immunity, and complement system. This could provide fresh possibilities for atherosclerosis research and treatment in the future.

Identification of a 10-mer peptide from the death domain of MyD88 which attenuates inflammation and insulin resistance and improves glucose metabolism

Insulin resistance (IR) is the key pathophysiological cause of type 2 diabetes, and inflammation has been implicated in it. The death domain (DD) of the adaptor protein, MyD88 plays a crucial role in the transduction of TLR4-associated inflammatory signal. Herein, we have identified a 10-residue peptide (M10), from the DD of MyD88 which seems to be involved in Myddosome formation. We hypothesized that M10 could inhibit MyD88-dependent TLR4-signaling and might have effects on inflammation-associated IR. Intriguingly, 10-mer M10 showed oligomeric nature and reversible self-assembly property indicating the peptide's ability to recognize its own amino acid sequence. M10 inhibited LPS-induced nuclear translocation of NF-κB in L6 myotubes and also reduced LPS-induced IL-6 and TNF-α production in peritoneal macrophages of BALB/c mice. Remarkably, M10 inhibited IL-6 and TNF-α secretion in diabetic, db/db mice. Notably, M10 abrogated IR in insulin-resistant L6 myotubes, which was associated with an increase in glucose uptake and a decrease in Ser307-phosphorylation of IRS1, TNF-α-induced JNK activation and nuclear translocation of NF-κB in these cells. Alternate day dosing with M10 (10 and 20 mg/kg) for 30 days in db/db mice significantly lowered blood glucose and improved glucose intolerance after loading, 3.0 g/kg glucose orally. Furthermore, M10 increased insulin and adiponectin secretion in db/db mice. M10-induced glucose uptake in L6 myotubes involved the activation of PI3K/AKT/GLUT4 pathways. A scrambled M10-analog was mostly inactive. Overall, the results show the identification of a 10-mer peptide from the DD of MyD88 with anti-inflammatory and anti-diabetic properties, suggesting that targeting of TLR4-inflammatory pathway, could lead to the discovery of molecules against IR and diabetes.

MyD88 in myofibroblasts enhances nonalcoholic fatty liver disease-related hepatocarcinogenesis via promoting macrophage M2 polarization

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a major cause of chronic liver diseases and has emerged as the leading factor in the pathogenesis of hepatocellular carcinoma (HCC). MyD88 contributes to the development of HCC. However, the underlying mechanism by which MyD88 in myofibroblasts regulates NAFLD-associated liver cancer development remains unknown.

RESULTS

Myofibroblast MyD88-deficient (SMAMyD88-/-) mice were protected from diet-induced obesity and developed fewer and smaller liver tumors. MyD88 deficiency in myofibroblasts attenuated macrophage M2 polarization and fat accumulation in HCC tissues. Mechanistically, MyD88 signaling in myofibroblasts enhanced CCL9 secretion, thereby promoting macrophage M2 polarization. This process may depend on the CCR1 receptor and STAT6/ PPARβ pathway. Furthermore, liver tumor growth was attenuated in mice treated with a CCR1 inhibitor. CCLl5 (homologous protein CCL9 in humans) expression was increased in myofibroblasts of HCC and was associated with shorter survival of patients with HCC. Thus, our results indicate that MyD88 in myofibroblasts promotes NAFLD-related HCC progression and may be a promising therapeutic target for HCC treatment.

CONCLUSION

This study demonstrates that MyD88 in myofibroblasts can promote nonalcoholic fatty liver disease-related hepatocarcinogenesis by enhancing macrophage M2 polarization, which might provide a potential molecular therapeutic target for HCC.

Sleep Deprivation Promotes Endothelial Inflammation and Atherogenesis by Reducing Exosomal miR-182-5p

BACKGROUND

Insufficient or disrupted sleep increases the risk of cardiovascular disease, including atherosclerosis. However, we know little about the molecular mechanisms by which sleep modulates atherogenesis. This study aimed to explore the potential role of circulating exosomes in endothelial inflammation and atherogenesis under sleep deprivation status and the molecular mechanisms involved.

METHODS

Circulating exosomes were isolated from the plasma of volunteers with or without sleep deprivation and mice subjected to 12-week sleep deprivation or control littermates. miRNA array was performed to determine changes in miRNA expression in circulating exosomes.

RESULTS

Although the total circulating exosome levels did not change significantly, the isolated plasma exosomes from sleep-deprived mice or human were a potent inducer of endothelial inflammation and atherogenesis. Through profiling and functional analysis of the global microRNA in the exosomes, we found miR-182-5p is a key exosomal cargo that mediates the proinflammatory effects of exosomes by upregulation of MYD88 (myeloid differentiation factor 88) and activation of NF-ĸB (nuclear factor kappa-B)/NLRP3 pathway in endothelial cells. Moreover, sleep deprivation or the reduction of melatonin directly decreased the synthesis of miR-182-5p and led to the accumulation of reactive oxygen species in small intestinal epithelium.

CONCLUSIONS

The findings illustrate an important role for circulating exosomes in distant communications, suggesting a new mechanism underlying the link between sleep disorder and cardiovascular disease.

New Insights into NF-κB Signaling in Innate Immunity: Focus on Immunometabolic Crosstalks

The nuclear factor kappa B (NF-κB) is a family of transcription factors that, beyond their numberless functions in various cell processes, play a pivotal role in regulating immune cell activation. Two main pathways-canonical and non-canonical-are responsible for NF-κB activation and heterodimer translocation into the nucleus. A complex crosstalk between NF-κB signaling and metabolism is emerging in innate immunity. Metabolic enzymes and metabolites regulate NF-κB activity in many cases through post-translational modifications such as acetylation and phosphorylation. On the other hand, NF-κB affects immunometabolic pathways, including the citrate pathway, thereby building an intricate network. In this review, the emerging findings about NF-κB function in innate immunity and the interplay between NF-κB and immunometabolism have been discussed. These outcomes allow for a deeper comprehension of the molecular mechanisms underlying NF-κB function in innate immune cells. Moreover, the new insights are important in order to perceive NF-κB signaling as a potential therapeutic target for inflammatory/immune chronic diseases.

MYD88 and Proinflammatory Chemokines in Aortic Atheromatosis: Exploring Novel Statin Effects

Atherosclerosis is driven by a diverse range of cellular and molecular processes. In the present study, we sought to better understand how statins mitigate proatherogenic inflammation. 48 male New Zealand rabbits were divided into eight groups, each including 6 animals. The control groups received normal chow for 90 and 120 days. Three groups underwent a hypercholesterolemic diet (HCD) for 30, 60, and 90 days. Another three groups underwent HCD for 3 months, followed by normal chow for one month, with or without rosuvastatin or fluvastatin. The cytokine and chemokine expressions were assessed in the samples of thoracic and abdominal aorta. Rosuvastatin significantly reduced MYD88, CCL4, CCL20, CCR2, TNF-α, IFN-β, IL-1b, IL-2, IL-4, IL-8, and IL-10, both in the thoracic and abdominal aorta. Fluvastatin also downregulated MYD88, CCR2, IFN-β, IFN-γ, IL-1b, IL-2, IL-4, and IL-10 in both aortic segments. Rosuvastatin curtailed the expression of CCL4, IFN-β, IL-2, IL-4, and IL-10 more effectively than fluvastatin in both types of tissue. MYD88, TNF-α, IL-1b, and IL-8 showed a stronger downregulation with rosuvastatin compared to fluvastatin only in the thoracic aorta. The CCL20 and CCR2 levels reduced more extensively with rosuvastatin treatment only in abdominal aortic tissue. In conclusion, statin therapy can halt proatherogenic inflammation in hyperlipidemic animals. Rosuvastatin may be more effective in downregulating MYD88 in atherosclerotic thoracic aortas.

Adipose tissue macrophages as potential targets for obesity and metabolic diseases

Macrophage infiltration into adipose tissue is a key pathological factor inducing adipose tissue dysfunction and contributing to obesity-induced inflammation and metabolic disorders. In this review, we aim to present the most recent research on macrophage heterogeneity in adipose tissue, with a focus on the molecular targets applied to macrophages as potential therapeutics for metabolic diseases. We begin by discussing the recruitment of macrophages and their roles in adipose tissue. While resident adipose tissue macrophages display an anti-inflammatory phenotype and promote the development of metabolically favorable beige adipose tissue, an increase in pro-inflammatory macrophages in adipose tissue has negative effects on adipose tissue function, including inhibition of adipogenesis, promotion of inflammation, insulin resistance, and fibrosis. Then, we presented the identities of the newly discovered adipose tissue macrophage subtypes (e.g. metabolically activated macrophages, CD9+ macrophages, lipid-associated macrophages, DARC+ macrophages, and MFehi macrophages), the majority of which are located in crown-like structures within adipose tissue during obesity. Finally, we discussed macrophage-targeting strategies to ameliorate obesity-related inflammation and metabolic abnormalities, with a focus on transcriptional factors such as PPARγ, KLF4, NFATc3, and HoxA5, which promote macrophage anti-inflammatory M2 polarization, as well as TLR4/NF-κB-mediated inflammatory pathways that activate pro-inflammatory M1 macrophages. In addition, a number of intracellular metabolic pathways closely associated with glucose metabolism, oxidative stress, nutrient sensing, and circadian clock regulation were examined. Understanding the complexities of macrophage plasticity and functionality may open up new avenues for the development of macrophage-based treatments for obesity and other metabolic diseases.

Potential roles of endothelial cells-related non-coding RNAs in cardiovascular diseases

Endothelial dysfunction is identified by a conversion of the endothelium toward decreased vasodilation and prothrombic features and is known as a primary pathogenic incident in cardiovascular diseases. An insight based on particular and promising biomarkers of endothelial dysfunction may possess vital clinical significances. Currently, non-coding RNAs due to their participation in critical cardiovascular processes like initiation and progression have gained much attention as possible diagnostic as well as prognostic biomarkers in cardiovascular diseases. Emerging line of proof has demonstrated that abnormal expression of non-coding RNAs is nearly correlated with the pathogenesis of cardiovascular diseases. In the present review, we focus on the expression and functional effects of various kinds of non-coding RNAs in cardiovascular diseases and negotiate their possible clinical implications as diagnostic or prognostic biomarkers and curative targets.

Neuroprotection by Preconditioning in Mice is Dependent on MyD88-Mediated CXCL10 Expression in Endothelial Cells

The central nervous system (CNS) can be preconditioned to resist damage by peripheral pretreatment with low-dose gram-negative bacterial endotoxin lipopolysaccharide (LPS). Underlying mechanisms associated with transient protection of the cerebral cortex against traumatic brain injury include increased neuronal production of antiapoptotic and neurotrophic molecules, microglial-mediated displacement of inhibitory presynaptic terminals innervating the soma of cortical projection neurons, and synchronized firing of cortical projection neurons. However, the cell types and signaling responsible for these neuronal and microglial changes are unknown. A fundamental question is whether LPS penetrates the CNS or acts on the luminal surface of brain endothelial cells, thereby triggering an indirect parenchymal neuroprotective response. The present study shows that a low-dose intraperitoneal LPS treatment increases brain endothelial cell activation markers CD54, but does not open the blood-brain barrier or alter brain endothelial cell tight junctions as assessed by electron microscopy. NanoString nCounter transcript analyses of CD31-positive brain endothelial cells further revealed significant upregulation of Cxcl10, C3, Ccl2, Il1β, Cxcl2, and Cxcl1, consistent with identification of myeloid differentiation primary response 88 (MyD88) as a regulator of these transcripts by pathway analysis. Conditional genetic endothelial cell gene ablation approaches demonstrated that both MyD88-dependent Toll-like receptor 4 (TLR4) signaling and Cxcl10 expression are essential for LPS-induced neuroprotection and microglial activation. These results suggest that C-X-C motif chemokine ligand 10 (CXCL10) production by endothelial cells in response to circulating TLR ligands may directly or indirectly signal to CXCR3 on neurons and/or microglia. Targeted activation of brain endothelial receptors may thus provide an attractive approach for inducing transient neuroprotection.

Adipose endothelial cells mastering adipose tissues metabolic fate

Dynamic communication within adipose tissue depends on highly vascularized structural characteristics to maintain systemic metabolic homoeostasis. Recently, it has been noted that adipose endothelial cells (AdECs) act as essential bridges for biological information transmission between adipose-resident cells. Hence, paracrine regulators that mediate crosstalk between AdECs and adipose stromal cells were summarized. We also highlight the importance of AdECs to maintain adipocytes metabolic homoeostasis by regulating insulin sensitivity, lipid turnover and plasticity. The differential regulation of AdECs in adipose plasticity often depends on vascular density and metabolic states. Although choosing pro-angiogenic or anti-angiogenic therapies for obesity is still a matter of debate in clinical settings, the growing numbers of drugs have been confirmed to play an anti-obesity effect by affecting vascularization. Pharmacologic angiogenesis intervention has great potential as therapeutic strategies for obesity.

Anti-inflammatory properties of lemon-derived extracellular vesicles are achieved through the inhibition of ERK/NF-κB signalling pathways

Chronic inflammation is associated with the occurrence of several diseases. However, the side effects of anti-inflammatory drugs prompt the identification of new therapeutic strategies. Plant-derived extracellular vesicles (PDEVs) are gaining increasing interest in the scientific community for their biological properties. We isolated PDEVs from the juice of Citrus limon L. (LEVs) and characterized their flavonoid, limonoid and lipid contents through reversed-phase high-performance liquid chromatography coupled to electrospray ionization quadrupole time-of-flight mass spectrometry (RP-HPLC-ESI-Q-TOF-MS). To investigate whether LEVs have a protective role on the inflammatory process, murine and primary human macrophages were pre-treated with LEVs for 24 h and then were stimulated with lipopolysaccharide (LPS). We found that pre-treatment with LEVs decreased gene and protein expression of pro-inflammatory cytokines, such as IL-6, IL1-β and TNF-α, and reduced the nuclear translocation and phosphorylation of NF-κB in LPS-stimulated murine macrophages. The inhibition of NF-κB activation was associated with the reduction in ERK1-2 phosphorylation. Furthermore, the ability of LEVs to decrease pro-inflammatory cytokines and increase anti-inflammatory molecules was confirmed ex vivo in human primary T lymphocytes. In conclusion, we demonstrated that LEVs exert anti-inflammatory effects both in vitro and ex vivo by inhibiting the ERK1-2/NF-κB signalling pathway.

IL-1R-IRAKM-Slc25a1 signaling axis reprograms lipogenesis in adipocytes to promote diet-induced obesity in mice

Toll-like receptors/Interleukin-1 receptor signaling plays an important role in high-fat diet-induced adipose tissue dysfunction contributing to obesity-associated metabolic syndromes. Here, we show an unconventional IL-1R-IRAKM-Slc25a1 signaling axis in adipocytes that reprograms lipogenesis to promote diet-induced obesity. Adipocyte-specific deficiency of IRAKM reduces high-fat diet-induced body weight gain, increases whole body energy expenditure and improves insulin resistance, associated with decreased lipid accumulation and adipocyte cell sizes. IL-1β stimulation induces the translocation of IRAKM Myddosome to mitochondria to promote de novo lipogenesis in adipocytes. Mechanistically, IRAKM interacts with and phosphorylates mitochondrial citrate carrier Slc25a1 to promote IL-1β-induced mitochondrial citrate transport to cytosol and de novo lipogenesis. Moreover, IRAKM-Slc25a1 axis mediates IL-1β induced Pgc1a acetylation to regulate thermogenic gene expression in adipocytes. IRAKM kinase-inactivation also attenuates high-fat diet-induced obesity. Taken together, our study suggests that the IL-1R-IRAKM-Slc25a1 signaling axis tightly links inflammation and adipocyte metabolism, indicating a potential therapeutic target for obesity.

Proteomic networks associated with tumor-educated macrophage polarization and cytotoxicity potentiated by heat-killed tuberculosis

Local administration of attenuated mycobacterium has been used as a cancer treatment adjuvant to re-boost patient immune responses with variable clinical outcomes. We aimed to clarify the impact of attenuated heat-killed tuberculosis (HKTB) on tumor-associated macrophages which play critical roles in shaping immunological regulation in the tumor microenvironment. Upon HKTB stimulation, both primary macrophages derived from the peripheral blood of healthy subjects and from lung cancer patients as well as THP1-derived classically activated macrophages (Ms) and tumor-educated macrophages (TEMs) were polarized into the proinflammatory phenotype, as characterized by increased expression cluster of differentiation 86. A quantitative proteomic analysis revealed that stimulated TEMs were unable to activate the toll-like receptor 2, signal transducer and activator of transcription 1, or nuclear factor-κB signaling. Instead, they showed distinct intercellular adhesion molecule 1 signaling, impaired cell adhesion, and mitochondrial dysfunction. These molecular mechanisms might contribute to lower cytotoxicity of HKTB-stimulated TEMs against A549 cells via the release of distinct inflammatory cytokines compared to HKTB-stimulated Ms. Our study provides an unbiased and systematic interpretation of cellular and molecular alterations of HKTB-reeducated macrophages which should help illuminate potential strategies of HKTB-stimulated macrophage-based combination therapy for cancer treatment.

CD38 deficiency protects the retina from ischaemia/reperfusion injury partly via suppression of TLR4/MyD88/NF-κB signalling

PURPOSE

This study aimed to explore cellular localisation of CD38 in the retina and evaluate the role and potential mechanism of CD38 deficiency in retinal ischaemia/reperfusion (I/R) injury.

METHODS

Six-to eight-week-old male CD38 knockout (KO) and wild-type mice in C57BL/6 background were used. Immunostaining was performed to determine the cellular localisation of CD38 in the retina. Haematoxylin and eosin staining and immunostaining of Brn3a were used to evaluate the retinal I/R injury. Western blotting was performed to detect toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), p-p65, ionised calcium-binding adapter molecule 1, Sirtuin1 (Sirt1), Ac-p65, and pro-inflammatory cytokines protein expression.

RESULTS

CD38 was highly expressed in mouse retinal microglia and astrocytes/Müller cells. CD38 deficiency reduced I/R-induced retinal damage and retinal ganglion cell death. Following retinal I/R injury, TLR4, MyD88, nuclear factor-κB p-p65 (NF-κB p-p65), pro-inflammatory cytokines and CD38 protein levels were also upregulated. After I/R injury, retinal inflammation factors IL-1β, IL-6, and TNF-α mRNA and protein levels were increased. IL-1β, IL-6, and TNF-α were reduced in CD38 KO mice after I/R injury. Retinal I/R injury induced the activation of microglia, but this effect was also suppressed by KO of CD38. Additionally, retinal I/R induced a significant increase in Ac-p65 protein levels and decrease in Sirt1 protein levels, while this effect was greatly attenuated by KO of CD38.

CONCLUSION

CD38 deficiency protects the retina from I/R injury by suppressing microglial activation partly via activating Sirt1-mediated suppression of TLR4/MyD88/NF-κB signalling.

Hydrolyzed Proteins and Vegetable Peptides: Anti-Inflammatory Mechanisms in Obesity and Potential Therapeutic Targets

Chronic low-grade inflammation is present in overweight and obesity, causing changes in several metabolic pathways. It impairs systemic functioning and positively feeds back the accumulation of more adipose tissue. Studies with hydrolyzed proteins and plant peptides have demonstrated a potential anti-inflammatory and immunomodulatory effect of these peptides. However, it is challenging and necessary to explore the mechanism of action of such molecules because understanding their effects depends on their structural characterizations. Furthermore, the structure might also give insights into safety, efficacy and efficiency, with a view of a possible health application. Thus, the present narrative review aimed to discuss the mechanisms of action of hydrolyzed proteins and plant peptides as anti-inflammatory agents in obesity. Keywords and related terms were inserted into databases for the search. Based on the studies evaluated, these biomolecules act by different pathways, favoring the reduction of inflammatory cytokines and adipokines and the polarization of macrophages to the M2 phenotype. Finally, as a future perspective, bioinformatics is suggested as a tool to help understand and better use these molecules considering their applicability in pre-clinical and clinical studies.

Endothelial Cell CD36 Reduces Atherosclerosis and Controls Systemic Metabolism

High-fat Western diets contribute to tissue dysregulation of fatty acid and glucose intake, resulting in obesity and insulin resistance and their sequelae, including atherosclerosis. New therapies are desperately needed to interrupt this epidemic. The significant idea driving this research is that the understudied regulation of fatty acid entry into tissues at the endothelial cell (EC) interface can provide novel therapeutic targets that will greatly modify health outcomes and advance health-related knowledge. Dysfunctional endothelium, defined as activated, pro-inflammatory, and pro-thrombotic, is critical in atherosclerosis initiation, in modulating thrombotic events that could result in myocardial infarction and stroke, and is a hallmark of insulin resistance. Dyslipidemia from high-fat diets overwhelmingly contributes to the development of dysfunctional endothelium. CD36 acts as a receptor for pathological ligands generated by high-fat diets and in fatty acid uptake, and therefore, it may additionally contribute to EC dysfunction. We created EC CD36 knockout (CD36°) mice using cre-lox technology and a cre-promoter that does not eliminate CD36 in hematopoietic cells (Tie2e cre). These mice were studied on different diets, and crossed to the low density lipoprotein receptor (LDLR) knockout for atherosclerosis assessment. Our data show that EC CD36° and EC CD36°/LDLR° mice have metabolic changes suggestive of an uncompensated role for EC CD36 in fatty acid uptake. The mice lacking expression of EC CD36 had increased glucose clearance compared with controls when fed with multiple diets. EC CD36° male mice showed increased carbohydrate utilization and decreased energy expenditure by indirect calorimetry. Female EC CD36°/LDLR° mice have reduced atherosclerosis. Taken together, these data support a significant role for EC CD36 in systemic metabolism and reveal sex-specific impact on atherosclerosis and energy substrate use.

MyD88: At the heart of inflammatory signaling and cardiovascular disease

Cardiovascular disease is a leading cause of death worldwide and is associated with systemic inflammation. In depth study of the cell-specific signaling mechanisms mediating the inflammatory response is vital to improving anti-inflammatory therapies that reduce mortality and morbidity. Cellular damage in the cardiovascular system results in the release of damage associated molecular patterns (DAMPs), also known as "alarmins," which activate myeloid cells through the adaptor protein myeloid differentiation primary response 88 (MyD88). MyD88 is broadly expressed in most cell types of the immune and cardiovascular systems, and its role often differs in a cardiovascular disease context and cell specific manner. Herein we review what is known about MyD88 in the setting of a variety of cardiovascular diseases, discussing cell specific functions and the relative contributions of MyD88-dependent vs. independent alarmin triggered inflammatory signaling. The widespread involvement of these pathways in cardiovascular disease, and their largely unexplored complexity, sets the stage for future in depth mechanistic studies that may place MyD88 in both immune and non-immune cell types as an attractive target for therapeutic intervention in cardiovascular disease.

Proteopathic tau primes and activates interleukin-1β via myeloid-cell-specific MyD88- and NLRP3-ASC-inflammasome pathway

Pathological hyperphosphorylation and aggregation of tau (pTau) and neuroinflammation, driven by interleukin-1β (IL-1β), are the major hallmarks of tauopathies. Here, we show that pTau primes and activates IL-1β. First, RNA-sequence analysis suggests paired-helical filaments (PHFs) from human tauopathy brain primes nuclear factor κB (NF-κB), chemokine, and IL-1β signaling clusters in human primary microglia. Treating microglia with pTau-containing neuronal media, exosomes, or PHFs causes IL-1β activation, which is NLRP3, ASC, and caspase-1 dependent. Suppression of pTau or ASC reduces tau pathology and inflammasome activation in rTg4510 and hTau mice, respectively. Although the deletion of MyD88 prevents both IL-1β expression and activation in the hTau mouse model of tauopathy, ASC deficiency in myeloid cells reduces pTau-induced IL-1β activation and improves cognitive function in hTau mice. Finally, pTau burden co-exists with elevated IL-1β and ASC in autopsy brains of human tauopathies. Together, our results suggest pTau activates IL-1β via MyD88- and NLRP3-ASC-dependent pathways in myeloid cells, including microglia.

Mitogen and Stress-Activated Kinases 1 and 2 Mediate Endothelial Dysfunction

Inflammation promotes endothelial dysfunction, but the underlying mechanisms remain poorly defined in vivo. Using translational vascular function testing in myocardial infarction patients, a situation where inflammation is prevalent, and knock-out (KO) mouse models we demonstrate a role for mitogen-activated-protein-kinases (MAPKs) in endothelial dysfunction. Myocardial infarction significantly lowers mitogen and stress kinase 1/2 (MSK1/2) expression in peripheral blood mononuclear cells and diminished endothelial function. To further understand the role of MSK1/2 in vascular function we developed in vivo animal models to assess vascular responses to vasoactive drugs using laser Doppler imaging. Genetic deficiency of MSK1/2 in mice increased plasma levels of pro-inflammatory cytokines and promoted endothelial dysfunction, through attenuated production of nitric oxide (NO), which were further exacerbated by cholesterol feeding. MSK1/2 are activated by toll-like receptors through MyD88. MyD88 KO mice showed preserved endothelial function and reduced plasma cytokine expression, despite significant hypercholesterolemia. MSK1/2 kinases interact with MAPK-activated proteins 2/3 (MAPKAP2/3), which limit cytokine synthesis. Cholesterol-fed MAPKAP2/3 KO mice showed reduced plasma cytokine expression and preservation of endothelial function. MSK1/2 plays a significant role in the development of endothelial dysfunction and may provide a novel target for intervention to reduce vascular inflammation. Activation of MSK1/2 could reduce pro-inflammatory responses and preserve endothelial vasodilator function before development of significant vascular disease.

Inhibition of MyD88 by LM8 Attenuates Obesity-Induced Cardiac Injury

Obesity-induced cardiomyopathy involves chronic and sustained inflammation. The toll-like receptor 4 (TLR4) signaling pathway can associate innate immunity with obesity. Myeloid differentiation primary response 88 (MyD88), an indispensable downstream adaptor molecule of TLR4, has been reported to mediate obesity complications. However, whether inhibition of MyD88 can mitigate obesity-induced heart injury remains unclear. LM8, a new MyD88 inhibitor, exhibits prominent anti-inflammatory activity in lipopolysaccharide-treated macrophages. In this study, the protective effects of LM8 on a high-fat diet (HFD)-induced heart injury were assessed in a mouse model of obesity. As suggested from the achieved results, LM8 treatment alleviated HFD-induced pathological and functional damages of the heart in mice. Meantime, the treatment of mice with LM8 could significantly inhibit myocardial hypertrophy, fibrosis, inflammatory cytokines expression, and inflammatory cell infiltration induced by HFD. Besides, LM8 administration inhibited the formation of MyD88/TLR4 complex, phosphorylation of ERK, and activation of nuclear factor-κB induced by HFD. According to the achieved results, MyD88 inhibitor LM8 ameliorated obesity-induced heart injury by inhibiting MyD88-ERK/nuclear factor-κB dependent cardiac inflammatory pathways. Furthermore, targeting MyD88 might be a candidate of a therapeutic method to treat obesity-induced heart injury.

Burn injury induces elevated inflammatory traffic: the role of NF-κB

A burn insult generally sustains a hypovolemic shock due to a significant loss of plasma from the vessels. The burn injury triggers the release of various mediators, such as reactive oxygen species (ROS), cytokines, and inflammatory mediators. Damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs), stemming from foreign microbial discharge and damaged tissue or necrotic cells from the burn-injured site, enter the systemic circulation, activate toll-like receptors (TLRs), and trigger the excessive secretion of cytokines and inflammatory mediators. Inflammation plays a vital role in remodeling an injured tissue, detoxifying toxins, and helps in the healing process. A transcription factor, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), contributes to a variety of physiological and pathological conditions, including immune response, cell death, cell survival, and inflammatory processes. During the pathogenesis of a burn wound, upregulation of various cytokines and growth factors lead to undesirable tissue inflammation. Thus, NF-κB, a dominant moderator of inflammation, needs to be altered to prove beneficial to the treatment of burns or other inflammation-associated diseases. This review addresses the relationship between NF-κB and elevated inflammation in a burn condition that could potentially be altered to induce an early wound-healing mechanism of burn wounds.

Synthetic immunomodulation with a CRISPR super-repressor in vivo

Transient modulation of the genes involved in immunity, without exerting a permanent change in the DNA code, can be an effective strategy to modulate the course of many inflammatory conditions. CRISPR-Cas9 technology represents a promising platform for achieving this goal. Truncation of guide RNA (gRNA) from the 5' end enables the application of a nuclease competent Cas9 protein for transcriptional modulation of genes, allowing multifunctionality of CRISPR. Here, we introduce an enhanced CRISPR-based transcriptional repressor to reprogram immune homeostasis in vivo. In this repressor system, two transcriptional repressors-heterochromatin protein 1 (HP1a) and Krüppel-associated box (KRAB)-are fused to the MS2 coat protein and subsequently recruited by gRNA aptamer binding to a nuclease competent CRISPR complex containing truncated gRNAs. With the enhanced repressor, we demonstrate transcriptional repression of the Myeloid differentiation primary response 88 (Myd88) gene in vitro and in vivo. We demonstrate that this strategy can efficiently downregulate Myd88 expression in lung, blood and bone marrow of Cas9 transgenic mice that receive systemic injection of adeno-associated virus (AAV)2/1-carrying truncated gRNAs targeting Myd88 and the MS2-HP1a-KRAB cassette. This downregulation is accompanied by changes in downstream signalling elements such as TNF-α and ICAM-1. Myd88 repression leads to a decrease in immunoglobulin G (IgG) production against AAV2/1 and AAV2/9 and this strategy modulates the IgG response against AAV cargos. It improves the efficiency of a subsequent AAV9/CRISPR treatment for repression of proprotein convertase subtilisin/kexin type 9 (PCSK9), a gene that, when repressed, can lower blood cholesterol levels. We also demonstrate that CRISPR-mediated Myd88 repression can act as a prophylactic measure against septicaemia in both Cas9 transgenic and C57BL/6J mice. When delivered by nanoparticles, this repressor can serve as a therapeutic modality to influence the course of septicaemia. Collectively, we report that CRISPR-mediated repression of endogenous Myd88 can effectively modulate the host immune response against AAV-mediated gene therapy and influence the course of septicaemia. The ability to control Myd88 transcript levels using a CRISPR-based synthetic repressor can be an effective strategy for AAV-based CRISPR therapies, as this pathway serves as a key node in the induction of humoral immunity against AAV serotypes.

IL-1 induces mitochondrial translocation of IRAK2 to suppress oxidative metabolism in adipocytes

Chronic inflammation is a common feature of obesity with elevated cytokines such as Interleukin-1 (IL-1) in circulation and tissues. Here, we report an unconventional IL-1R-MyD88-IRAK2-PHB/OPA1 signaling axis that reprograms mitochondrial metabolism in adipocytes to exacerbate obesity. IL-1 induced recruitment of IRAK2-Myddosome to mitochondria outer membrane via recognition by TOM20, followed by TIMM50-guided translocation of IRAK2 into mitochondria inner membrane to suppress oxidative phosphorylation and fatty acid oxidation, thereby, attenuating energy expenditure. Adipocyte-specific MyD88 or IRAK2 deficiency reduced high fat diet (HFD)-induced weight gain, increased energy expenditure and ameliorated insulin resistance, associated with a smaller adipocyte size and increased cristae formation. IRAK2 kinase inactivation also reduced HFD-induced metabolic diseases. Mechanistically, IRAK2 suppressed respiratory super-complex formation via interaction with PHB1 and OPA1 upon stimulation of IL-1. Taken together, our results suggest that IRAK2 Myddosome functions as a critical link between inflammation and metabolism, representing a novel therapeutic target for patients with obesity.

Analysis of Differentially Expressed Genes and Molecular Pathways in Familial Hypercholesterolemia Involved in Atherosclerosis: A Systematic and Bioinformatics Approach

Background and Aims: Familial hypercholesterolemia (FH) is one of the major risk factor for the progression of atherosclerosis and coronary artery disease. This study focused on identifying the dysregulated molecular pathways and core genes that are differentially regulated in FH and to identify the possible genetic factors and potential underlying mechanisms that increase the risk to atherosclerosis in patients with FH. Methods: The Affymetrix microarray dataset (GSE13985) from the GEO database and the GEO2R statistical tool were used to identify the differentially expressed genes (DEGs) from the white blood cells (WBCs) of five heterozygous FH patients and five healthy controls. The interaction between the DEGs was identified by applying the STRING tool and visualized using Cytoscape software. MCODE was used to determine the gene cluster in the interactive networks. The identified DEGs were subjected to the DAVID v6.8 webserver and ClueGo/CluePedia for functional annotation, such as gene ontology (GO) and enriched molecular pathway analysis of DEGs. Results: We investigated the top 250 significant DEGs (p-value < 0.05; fold two change ≥ 1 or ≤ -1). The GO analysis of DEGs with significant differences revealed that they are involved in critical biological processes and molecular pathways, such as myeloid cell differentiation, peptidyl-lysine modification, signaling pathway of MyD88-dependent Toll-like receptor, and cell-cell adhesion. The analysis of enriched KEGG pathways revealed the association of the DEGs in ubiquitin-mediated proteolysis and cardiac muscle contraction. The genes involved in the molecular pathways were shown to be differentially regulated by either activating or inhibiting the genes that are essential for the canonical signaling pathways. Our study identified seven core genes (UQCR11, UBE2N, ADD1, TLN1, IRAK3, LY96, and MAP3K1) that are strongly linked to FH and lead to a higher risk of atherosclerosis. Conclusion: We identified seven core genes that represent potential molecular biomarkers for the diagnosis of atherosclerosis and might serve as a platform for developing therapeutics against both FH and atherosclerosis. However, functional studies are further needed to validate their role in the pathogenesis of FH and atherosclerosis.

SBP2 deficiency in adipose tissue macrophages drives insulin resistance in obesity

Proinflammatory activation and accumulation of adipose tissue macrophages (ATMs) are associated with increased risk of insulin resistance in obesity. Here, we described the previously unidentified role of selenocysteine insertion sequence-binding protein 2 (SBP2) in maintaining insulin sensitivity in obesity. SBP2 was suppressed in ATMs of diet-induced obese mice and was correlated with adipose tissue inflammation. Loss of SBP2 initiated metabolic activation of ATMs, inducing intracellular reactive oxygen species content and inflammasome, which subsequently promoted IL-1β-associated local proliferation and infiltration of proinflammatory macrophages. ATM-specific knockdown of SBP2 in obese mice promoted insulin resistance by increasing fat tissue inflammation and expansion. Reexpression of SBP2 improved insulin sensitivity. Last, an herbal formula that specifically induced SBP2 expression in ATMs can experimentally improve insulin sensitivity. Clinical observation revealed that it improved hyperglycemia in patients with diabetes. This study identified SBP2 in ATMs as a potential target in rescuing insulin resistance in obesity.

Chlamydia and Lipids Engage a Common Signaling Pathway That Promotes Atherogenesis

BACKGROUND

Recent studies indicate that Toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88) signaling promote the development of high fat diet-induced atherosclerosis in hypercholesterolemic mice.

OBJECTIVES

The authors investigated the role of TLR4/MyD88 signaling in hematopoietic and stromal cells in the development and infection-mediated acceleration of atherosclerosis.

METHODS

The authors generated bone marrow chimeras between wild-type and Tlr4^-/- mice, as well as wild-type and Myd88^-/- mice. All mice were on the Apoe^-/- background and fed high fat diet. The authors infected the chimeric mice with C. pneumoniae (CP) and fed them high fat diet.

RESULTS

Aortic sinus plaques and lipid content were significantly reduced in Apoe^-/- mice that received Tlr4^-/-or Myd88^-/- bone marrow compared with control animals despite similar cholesterol levels. Similarly, Tlr4 or Myd88 deficiency in stromal cells also led to a reduction in the lesion area and lipid in aortic sinus plaques. MyD88 expression only in CD11c+ dendritic cells (myeloid cells) in cells was sufficient in otherwise MyD88-deficient mice to induce CP infection-mediated acceleration of atherosclerosis, underlining the key role of MyD88 in CD11c+ dendritic cells (myeloid cells). Whereas CP infection markedly accelerated atherosclerosis in TLR4- or MyD88-positive chimeras, CP infection had a minimal effect on atherosclerosis in TLR4- or MyD88-deficient mice (either in the hematopoietic or stromal cell compartments).

CONCLUSIONS

The authors show that both CP infection and metabolic stress associated with dyslipidemia use the same innate immune response pathway, utilizing TLR4/MyD88 signaling, with similar relative contributions in bone marrow-derived hematopoietic cells and in stromal cells. Further studies are required to understand this intricate and complex cross talk among innate and adaptive immune systems in various conditions to more effectively design dendritic cell-mediated atheroprotective vaccines and other therapeutic strategies.

Overweight/obesity affects histological features and inflammatory gene signature of synovial membrane of Rheumatoid Arthritis

Overweight/obesity influence disease burden and clinical outcome of Rheumatoid Arthritis (RA). The impact of overweight/obesity on synovial tissue (ST) inflammation is largely unknown. Here, we investigated the histological and transcriptional signature of ST obtained from RA in different disease phases (disease onset, failure to first-line conventional DMARDs and in sustained clinical and ultrasound remission) finding that overweight/obese DMARDs naive RA showed higher likelihood of follicular synovitis, higher IHC scores for sublining inflammatory cells (CD68⁺, CD21⁺ and CD20⁺) and higher IL-1RA plasma levels than normal weight RA. Regardless to the synovitis pattern, overweight/obese DMARDs naive RA showed a worse clinical response to “Treat-to-target” (T2T) than normal weight RA at 6 and 12 months follow-up. Conversely, MTX-IR RA did not show significant differences in synovial inflammation based on BMI category. Overweight/obese RA in stable clinical and US remission showed higher degree of residual synovitis in terms of sublining CD68⁺, CD20⁺ cells and lining and sublining CD3⁺ compared to normal weight RA. Finally, gene expression profile analysis revealed that ST of overweight/obese DMARDs naive RA is enriched by CCL3 and MyD88 compared to normal weight RA in sustained disease remission, the latter correlating with BMI and IHC scores for synovial CD68⁺ cells. These findings suggest that indeed overweight/obese RA show higher degree of synovitis at disease onset and after remission achievement that influences the response rate to T2T and should be considered within the management of patients with RA.

Loss of transglutaminase 2 sensitizes for diet-induced obesity-related inflammation and insulin resistance due to enhanced macrophage c-Src signaling

Transglutaminase 2 (TG2) is a multifunctional protein that promotes clearance of apoptotic cells (efferocytosis) acting as integrin β₃ coreceptor. Accumulating evidence indicates that defective efferocytosis contributes to the development of chronic inflammatory diseases. Obesity is characterized by the accumulation of dead adipocytes and inflammatory macrophages in the adipose tissue leading to obesity-related metabolic syndrome. Here, we report that loss of TG2 from bone marrow-derived cells sensitizes for high fat diet (HFD)-induced pathologies. We find that metabolically activated TG2 null macrophages express more phospho-Src and integrin β₃, unexpectedly clear dying adipocytes more efficiently via lysosomal exocytosis, but produce more pro-inflammatory cytokines than the wild type ones. Anti-inflammatory treatment with an LXR agonist reverts the HFD-induced phenotype in mice lacking TG2 in bone marrow-derived cells with less hepatic steatosis than in wild type mice proving enhanced lipid clearance. Thus it is interesting to speculate whether LXR agonist treatment together with enhancing lysosomal exocytosis could be a beneficial therapeutic strategy in obesity.

Innate Immune Signaling and Its Role in Metabolic and Cardiovascular Diseases

The innate immune system is an evolutionarily conserved system that senses and defends against infection and irritation. Innate immune signaling is a complex cascade that quickly recognizes infectious threats through multiple germline-encoded cell surface or cytoplasmic receptors and transmits signals for the deployment of proper countermeasures through adaptors, kinases, and transcription factors, resulting in the production of cytokines. As the first response of the innate immune system to pathogenic signals, inflammatory responses must be rapid and specific to establish a physical barrier against the spread of infection and must subsequently be terminated once the pathogens have been cleared. Long-lasting and low-grade chronic inflammation is a distinguishing feature of type 2 diabetes and cardiovascular diseases, which are currently major public health problems. Cardiometabolic stress-induced inflammatory responses activate innate immune signaling, which directly contributes to the development of cardiometabolic diseases. Additionally, although the innate immune elements are highly conserved in higher-order jawed vertebrates, lower-grade jawless vertebrates lack several transcription factors and inflammatory cytokine genes downstream of the Toll-like receptors (TLRs) and retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) pathways, suggesting that innate immune signaling components may additionally function in an immune-independent way. Notably, recent studies from our group and others have revealed that innate immune signaling can function as a vital regulator of cardiometabolic homeostasis independent of its immune function. Therefore, further investigation of innate immune signaling in cardiometabolic systems may facilitate the discovery of new strategies to manage the initiation and progression of cardiometabolic disorders, leading to better treatments for these diseases. In this review, we summarize the current progress in innate immune signaling studies and the regulatory function of innate immunity in cardiometabolic diseases. Notably, we highlight the immune-independent effects of innate immune signaling components on the development of cardiometabolic disorders.

CD36 mediates albumin transcytosis by dermal but not lung microvascular endothelial cells: role in fatty acid delivery

In healthy blood vessels, albumin crosses the endothelium to leave the circulation by transcytosis. However, little is known about the regulation of albumin transcytosis or how it differs in different tissues; its physiological purpose is also unclear. Using total internal reflection fluorescence microscopy, we quantified transcytosis of albumin across primary human microvascular endothelial cells from both lung and skin. We then validated our in vitro findings using a tissue-specific knockout mouse model. We observed that albumin transcytosis was saturable in the skin but not the lung microvascular endothelial cells, implicating a receptor-mediated process. We identified the scavenger receptor CD36 as being both necessary and sufficient for albumin transcytosis across dermal microvascular endothelium, in contrast to the lung where macropinocytosis dominated. Mutations in the apical helical bundle of CD36 prevented albumin internalization by cells. Mice deficient in CD36 specifically in endothelial cells exhibited lower basal permeability to albumin and less basal tissue edema in the skin but not in the lung. Finally, these mice also exhibited a smaller subcutaneous fat layer despite having identical total body weights and circulating fatty acid levels as wild-type animals. In conclusion, CD36 mediates albumin transcytosis in the skin but not the lung. Albumin transcytosis may serve to regulate fatty acid delivery from the circulation to tissues.

Development of a Novel Backbone Cyclic Peptide Inhibitor of the Innate Immune TLR/IL1R Signaling Protein MyD88

MyD88 is a cytoplasmic adaptor protein that plays a central role in signaling downstream of the TLRs and the IL1R superfamily. We previously demonstrated that MyD88 plays a critical role in EAE, the murine model of multiple sclerosis, and showed that the MyD88 BB-loop decoy peptide RDVLPGT ameliorates EAE. We now designed and screened a library of backbone cyclized peptides based on the linear BB loop peptide, to identify a metabolically stable inhibitor of MyD88 that retains the binding properties of the linear peptide. We identified a novel cyclic peptide protein mimetic that inhibits inflammatory responses to TLR ligands, and NFκB activation in response to IL-1 activation. The inhibitor, c(MyD 4-4), is metabolically stable in comparison to the linear peptide, blocks MyD88 in a specific manner, and inhibits MyD88 function by preventing MyD88 dimerization. Finally, treatment of mice with c(MyD 4-4) reduced the severity of clinical disease in the murine EAE model of multiple sclerosis. Thus, modulation of MyD88-dependent signaling using c(MyD 4-4) is a potential therapeutic strategy to lower innate immune inflammation in autoimmune CNS disease.

Intestinal epithelial Toll-like receptor 4 prevents metabolic syndrome by regulating interactions between microbes and intestinal epithelial cells in mice

Little is known about the pathogenesis of metabolic syndrome, although Toll-like receptor 4 (TLR4) has been implicated. We investigated whether TLR4 in the intestinal epithelium regulates metabolic syndrome by coordinating interactions between the luminal microbiota and host genes that regulate metabolism. Mice lacking TLR4 in the intestinal epithelium (TLR4^ΔIEC), but not mice lacking TLR4 in myeloid cells nor mice lacking TLR4 globally, developed metabolic syndrome; these features were not observed in TLR4^ΔIEC mice given antibiotics. Metagenomic analysis of the fecal microbiota revealed differences between TLR4^ΔIEC and wild-type mice, while meta-transcriptome analysis of the microbiota showed that intestinal TLR4 affected the expression of microbial genes involved in the metabolism of lipids, amino acids, and nucleotides. Genes regulated by peroxisome proliferator-activated receptors (PPARs) and the antimicrobial peptide lysozyme were significantly downregulated in TLR4^ΔIEC mice, suggesting a mechanism by which intestinal TLR4 could exert its effects on the microbiota and metabolic syndrome. Supportingly, antibiotics prevented both downregulation of PPAR genes and the development of metabolic syndrome, while PPAR agonists prevented development of metabolic syndrome in TLR4^ΔIEC mice. Thus, intestinal epithelial TLR4 regulates metabolic syndrome through altered host-bacterial signaling, suggesting that microbial or PPAR-based strategies might have therapeutic potential for this disease.

TLR4, TRIF, and MyD88 are essential for myelopoiesis and CD11c+ adipose tissue macrophage production in obese mice

Obesity-induced chronic inflammation is associated with metabolic disease. Results from mouse models utilizing a high-fat diet (HFD) have indicated that an increase in activated macrophages, including CD11c⁺ adipose tissue macrophages (ATMs), contributes to insulin resistance. Obesity primes myeloid cell production from hematopoietic stem cells (HSCs) and Toll-like receptor 4 (TLR4), and the downstream TIR domain-containing adapter protein-inducing interferon-β (TRIF)- and MyD88-mediated pathways regulate production of similar myeloid cells after lipopolysaccharide stimulation. However, the role of these pathways in HFD-induced myelopoiesis is unknown. We hypothesized that saturated fatty acids and HFD alter myelopoiesis by activating TLR4 pathways in HSCs, differentially producing pro-inflammatory CD11c⁺ myeloid cells that contribute to obesity-induced metabolic disease. Results from reciprocal bone marrow transplants (BMTs) with Tlr4^-/- and WT mice indicated that TLR4 is required for HFD-induced myelopoiesis and production of CD11c⁺ ATMs. Experiments with homozygous knockouts of Irakm (encoding a suppressor of MyD88 inactivation) and Trif in competitive BMTs revealed that MyD88 is required for HFD expansion of granulocyte macrophage progenitors and that Trif is required for pregranulocyte macrophage progenitor expansion. A comparison of WT, Tlr4^-/-, Myd88^-/-, and Trif^-/- mice on HFD demonstrated that TLR4 plays a role in the production of CD11c⁺ ATMs, and both Myd88^-/- and Trif^-/- mice produced fewer ATMs than WT mice. Moreover, HFD-induced TLR4 activation inhibited macrophage proliferation, leading to greater accumulation of recruited CD11c⁺ ATMs. Our results indicate that HFD potentiates TLR4 and both its MyD88- and TRIF-mediated downstream pathways within progenitors and adipose tissue and leads to macrophage polarization.

The role of the lipidome in obesity-mediated colon cancer risk

Obesity is a state of chronic inflammation influenced by lipids such as fatty acids and their secondary oxygenated metabolites deemed oxylipids. Many such lipid mediators serve as potent signaling molecules of inflammation, which can further alter lipid metabolism and lead to carcinogenesis. For example, sphingosine-1-phosphate activates cyclooxygenase-2 in endothelial cells resulting in the conversion of arachidonic acid (AA) to prostaglandin E₂ (PGE₂). PGE₂ promotes colon cancer cell growth. In contrast, the less studied path of AA oxygenation via cytochrome p450 enzymes produces epoxyeicosatetraenoic acids (EETs), whose anti-inflammatory properties cause shrinking of enlarged adipocytes, a characteristic of obesity, through the liberation of fatty acids. It is now thought that EET depletion occurs in obesity and may contribute to colon cell carcinogenesis. Meanwhile, gangliosides, a type of sphingolipid, are cell surface signaling molecules that contribute to the apoptosis of colon tumor cells. Many of these discoveries have been made recently and the mechanisms are still not fully understood, leading to an exciting new chapter of lipidomic research. In this review, mechanisms behind obesity-associated colon cancer are discussed with a focus on the role of small lipid signaling molecules in the process. Specifically, changes in lipid metabolite levels during obesity and the development of colon cancer, as well as novel biomarkers and targets for therapy, are discussed.

Cre Driver Mice Targeting Macrophages

The Cre/loxP system is a widely applied technology for site-specific genetic manipulation in mice. This system allows for deletion of the genes of interest in specific cells, tissues, and whole organism to generate a diversity of conditional knockout mouse strains. Additionally, the Cre/loxP system is useful for development of cell- and tissue-specific reporter mice for lineage tracing, and cell-specific conditional depletion models in mice. Recently, the Cre/loxP technique was extensively adopted to characterize the monocyte/macrophage biology in mouse models. Compared to other relatively homogenous immune cell types such as neutrophils, mast cells, and basophils, monocytes/macrophages represent a highly heterogeneous population which lack specific markers or transcriptional factors. Though great efforts have been made toward establishing macrophage-specific Cre driver mice in the past decade, all of the current available strains are not perfect with regard to their depletion efficiency and targeting specificity for endogenous macrophages. Here we overview the commonly used Cre driver mouse strains targeting macrophages and discuss their major applications and limitations.

Macrophage-Associated Lipin-1 Enzymatic Activity Contributes to Modified Low-Density Lipoprotein-Induced Proinflammatory Signaling and Atherosclerosis

OBJECTIVE

Macrophage proinflammatory responses induced by modified low-density lipoproteins (modLDL) contribute to atherosclerotic progression. How modLDL causes macrophages to become proinflammatory is still enigmatic. Macrophage foam cell formation induced by modLDL requires glycerolipid synthesis. Lipin-1, a key enzyme in the glycerolipid synthesis pathway, contributes to modLDL-elicited macrophage proinflammatory responses in vitro. The objective of this study was to determine whether macrophage-associated lipin-1 contributes to atherogenesis and to assess its role in modLDL-mediated signaling in macrophages.

APPROACH AND RESULTS

We developed mice lacking lipin-1 in myeloid-derived cells and used adeno-associated viral vector 8 expressing the gain-of-function mutation of mouse proprotein convertase subtilisin/kexin type 9 (adeno-associated viral vector 8-proprotein convertase subtilisin/kexin type 9) to induce hypercholesterolemia and plaque formation. Mice lacking myeloid-associated lipin-1 had reduced atherosclerotic burden compared with control mice despite similar plasma lipid levels. Stimulation of bone marrow-derived macrophages with modLDL activated a persistent protein kinase Cα/βII-extracellular receptor kinase1/2-jun proto-oncogene signaling cascade that contributed to macrophage proinflammatory responses that was dependent on lipin-1 enzymatic activity.

CONCLUSIONS

Our data demonstrate that macrophage-associated lipin-1 is atherogenic, likely through persistent activation of a protein kinase Cα/βII-extracellular receptor kinase1/2-jun proto-oncogene signaling cascade that contributes to foam cell proinflammatory responses. Taken together, these results suggest that modLDL-induced foam cell formation and modLDL-induced macrophage proinflammatory responses are not independent consequences of modLDL stimulation but rather are both directly influenced by enhanced lipid synthesis.

Mesenchymal Cell-Specific MyD88 Signaling Promotes Systemic Dissemination of Salmonella Typhimurium via Inflammatory Monocytes

Enteric pathogens including Salmonella enteric serovar Typhimurium can breach the epithelial barrier of the host and spread to systemic tissues. In response to infection, the host activates innate immune receptors via the signaling molecule MyD88, which induces protective inflammatory and antimicrobial responses. Most of these innate immune responses have been studied in hematopoietic cells, but the role of MyD88 signaling in other cell types remains poorly understood. Surprisingly, we found that Dermo1-Cre;Myd88fl/fl mice with mesenchymal cell-specific deficiency of MyD88 were less susceptible to orogastric and i.p. STyphimurium infection than their Myd88fl/fl littermates. The reduced susceptibility of Dermo1-Cre;Myd88fl/fl mice to infection was associated with lower loads of S. Typhimurium in the liver and spleen. Mutant analyses revealed that S. Typhimurium employs its virulence type III secretion system 2 to promote its growth through MyD88 signaling pathways in mesenchymal cells. Inflammatory monocytes function as a major cell population for systemic dissemination of S. Typhimurium Mechanistically, mesenchymal cell-specific MyD88 signaling promoted CCL2 production in the liver and spleen and recruitment of inflammatory monocytes to systemic organs in response to STyphimurium infection. Consistently, MyD88 signaling in mesenchymal cells enhanced the number of phagocytes including Ly6ChiLy6G- inflammatory monocytes harboring STyphimurium in the liver. These results suggest that S. Typhimurium promotes its systemic growth and dissemination through MyD88 signaling pathways in mesenchymal cells.

NF-κB signaling in inflammation

The transcription factor NF-κB regulates multiple aspects of innate and adaptive immune functions and serves as a pivotal mediator of inflammatory responses. NF-κB induces the expression of various pro-inflammatory genes, including those encoding cytokines and chemokines, and also participates in inflammasome regulation. In addition, NF-κB plays a critical role in regulating the survival, activation and differentiation of innate immune cells and inflammatory T cells. Consequently, deregulated NF-κB activation contributes to the pathogenic processes of various inflammatory diseases. In this review, we will discuss the activation and function of NF-κB in association with inflammatory diseases and highlight the development of therapeutic strategies based on NF-κB inhibition.

Can Parasitic Worms Cure the Modern World's Ills?

There has been increasing recognition that the alarming surge in allergy and autoimmunity in the industrialised and developing worlds shadows the rapid eradication of pathogens, such as parasitic helminths. Appreciation of this has fuelled an explosion in research investigating the therapeutic potential of these worms. This review considers the current state-of-play with a particular focus on exciting recent advances in the identification of potential novel targets for immunomodulation that can be exploited therapeutically. Furthermore, we contemplate the prospects for designing worm-derived immunotherapies for an ever-widening range of inflammatory diseases, including, for example, obesity, cardiovascular disease, and ageing as well as neurodevelopmental disorders like autism.

Myeloid-MyD88 Contributes to Ethanol-Induced Liver Injury in Mice Linking Hepatocellular Death to Inflammation

BACKGROUND

Toll-like receptor 4 (TLR4) is critical for ethanol (EtOH)-induced liver injury. TLR4 signaling is mediated by 2 proximal adaptor molecules: myeloid differentiation primary response protein (MyD88) and TLR-domain-containing adaptor-inducing interferon-β (TRIF). Studies utilizing global knockouts of MyD88 and TRIF identified a predominant role for TRIF signaling in the progression of EtOH-induced liver injury. In contrast, IL-1 receptor, which signals solely via the MyD88 pathway, is also known to mediate EtOH-induced liver injury. We postulated that a cell-specific role for MyD88 in myeloid cells might explain these apparently discrepant roles of MyD88. Here we made use of myeloid-specific MyD88-deficient (MyD88LysM-KO ) mice generated by crossing LysM-CRE mice with MyD88fl/fl mice to test this hypothesis.

METHODS

MyD88LysM-KO and littermate controls were fed a Lieber-DeCarli EtOH-containing diet or pair-fed control diets for 25 days.

RESULTS

Littermate control, but not MyD88LysM-KO , mice developed early stages of EtOH-induced liver injury including elevated plasma alanine aminotransferase and increased hepatic triglycerides. Lobular inflammation and expression of pro-inflammatory cytokines/chemokines was increased in control but not MyD88LysM-KO . Further, EtOH-induced inflammasome activation, indicated by the presence of cleaved caspase-1 and mature IL-1β protein, was also ameliorated in livers of MyD88LysM-KO mice. In contrast, chronic EtOH-induced apoptosis, assessed via TUNEL staining, was independent of myeloid-MyD88 expression.

CONCLUSIONS

Collectively, these data demonstrate a cell-specific role for MyD88 in the development of chronic EtOH-induced liver injury. While MyD88LysM-KO still exhibited hepatocellular apoptosis in response to chronic EtOH, the absence of MyD88 on myeloid cells prevented the development of hepatic steatosis and inflammation.

From Christian de Duve to Yoshinori Ohsumi: More to autophagy than just dining at home

Christian de Duve first coined the expression “autophagy” during his seminal work on the discovery of lysosomes, which led to him being awarded the Nobel Prize in Physiology or Medicine in 1974. The term was adopted to distinguish degradation of intracellular components from the uptake and degradation of extracellular substances that he called “heterophagy”. Studies until the 1990s were largely observational/morphological-based until in 1993 Yoshinori Oshumi described a genetic screen in yeast undergoing nitrogen deprivation that led to the isolation of autophagy-defective mutants now better known as ATG (AuTophaGy-related) genes. The screen identified mutants that fell into 15 complementation groups implying that at least 15 genes were involved in the regulation of autophagy in yeast undergoing nutrient deprivation, but today, 41 yeast ATG genes have been described and many (though not all) have orthologues in humans. Attempts to identify the genetic basis of autophagy led to an explosion in its research and it's not surprising that in 2016 Yoshinori Oshumi was awarded the Nobel Prize in Physiology or Medicine. Our aim here is not to exhaustively review the ever-expanding autophagy literature (>60 papers per week), but to celebrate Yoshinori Oshumi's Nobel Prize by highlighting just a few aspects that are not normally extensively covered. In an accompanying mini-review we address the role of autophagy in early-diverging eukaryote parasites that like yeast, lack lysosomes and so use a digestive vacuole to degrade autophagosome cargo and also discuss how parasitized host cells react to infection by subverting regulation of autophagy.